1. Field of the Invention
The present invention relates to a vacuum processing apparatus, and also relates to a vacuum processing apparatus equipped with a gate valve for airtightly sealing or opening a gate for communicating the inside and the outside of a vacuum vessel in which a sample is processed.
2. Description of the Related Art
In the field of apparatuses for processing an object in a decompressed chamber, such as the one mentioned above, there is a demand for improving the efficiency for processing the substrate being the object of processing, in addition to enhancing the minuteness and preciseness of the process. Therefore, in recent years, a multi-chamber apparatus has been developed in which a plurality of processing chambers are connected and combined as a single apparatus, enabling various processes to be performed to the substrate in a single apparatus, and improving the process efficiency.
In such an apparatus having plural processing chambers, each of the processing chambers are connected to a transfer chamber capable of having its inner gas or pressure controlled, which is equipped with a robot arm or the like for transferring the substrate inside thereof.
According to such structure, the pre-processed or post-processed substrate is transferred through the transfer chamber having its interior evacuated or supplied with inert gas from one processing chamber to another processing chamber, so that the substrate is subjected to continuous processing without being in contact with atmosphere outside. Thus, the contamination of the substrate is suppressed and the yield or efficiency of the process is improved.
Further, the time for increasing/decreasing the pressure in the processing chambers or the transfer chamber can be omitted or reduced, by which the processing steps are shortened and the work and time required for the overall substrate processing are reduced, and the processing efficiency is thereby improved.
According further to such apparatus, each processing chamber is detachably attached to the apparatus, so that by replacing the processing chambers or by changing the combination thereof, the apparatus can correspond to perform a new process without having to replace the whole apparatus. As a result, the costs for manufacturing products by processing the substrates in the apparatus can be cut down.
A known valve device called a gate valve for airtightly closing and opening an opening (gate) disposed with the chamber through which the sample is taken in and out of the processing chamber or the transfer chamber includes a valve body attached to an end of a beam-shaped member such as a shaft that is connected to a drive device such as an actuator. In such a gate valve, when the gate is to be closed, the actuator drives the valve body toward the opening while maintaining a predetermined distance with the surface of the chamber wall on which the gate is disposed, and when the valve body reaches a position substantially confronting the gate opening, the valve body is moved toward the opening until one surface of the valve body connects to the chamber wall or the gate opening.
In the above-mentioned arrangement, a seal member is disposed on one surface of the valve body for airtightly sealing the area between the valve body and the chamber wall or the gate opening. In the seal member, a dent or groove is disposed that extends to cover the whole length of the connection surface (seal surface) of the valve body which is to be sealed, and the seal member having elasticity is fit into this groove so that the seal member is positioned correctly and is prevented from being displaced on the valve body. The seal member disposed on the surface of the valve body is pressed against the wall or the opening to seal the space therebetween, and the seal member is also pressed against the surface of the dent or the groove to seal the space therebetween.
When opening the gate, the actuator moves the valve body being connected to the wall or the opening away from the gate. After separating the valve body from the chamber wall or opening, the valve body is moved away from the opening while maintaining a predetermined distance from the chamber wall, similar to when closing the gate.
Japanese Patent Application Laid-Open Publication Nos. 2002-276825 and H08-060374 disclose prior art gate valves of the type described above. Further, Japanese Patent Application Laid-Open Publication No. 2002-81555 discloses a prior art sealing means.
The prior art apparatuses had the following drawbacks. According to the prior art gate valve, when moving the valve body of the gate valve away from the gate opening, since the valve body is connected to the opening with high pressing force, the seal portion of the valve body may not be removed in uniform fashion, or large force must be applied when removing the seal, by which the valve body is vibrated by the shock of removal from the gate. This causes deposits such as reaction products attached to the process chamber wall or the surface of the valve during processing to fall by the vibration onto the sample and causing contamination or corrosion of the sample, or causes contamination of the members inside the processing chamber.
Thus, it is necessary to reduce vibration during movement of the valve body, but the prior art disclosures lack to provide sufficient measures.
According further to the gate valve of the prior art, the valve body is moved toward the opening until the valve body contacts the opening or the wall surface surrounding the opening, or the valve body is moved away therefrom, but if the valve body is designed to move along a guide such as a rail disposed in the direction of movement thereof, the gap disposed between the guide and the member being guided or the friction therebetween causes the valve body to vibrate.
Furthermore, as described above, a seal member having elasticity is disposed on the surface of the valve body of the gate valve coming into contact with the chamber wall or the opening, which covers the whole length surrounding the area to be sealed. However, according to the prior art, the seal member was positioned by fitting the seal member in the groove or dent disposed in the valve body, and the fitting of the seal member required time and work, so the time required for maintenance and testing operations was increased, and the overall operation efficiency of the apparatus was deteriorated.
Even further, the seal member is normally ring-shaped with a round cross-section, but while fitting the seal member into the groove or dent, the seal member may be twisted and rotated, and if the seal is connected in that state to the wall surface or opening, the deformation by the twist may prevent sufficient seal from being created, or cause the seal performance to be varied in various areas of the connecting surface, deteriorating the sealing performance. Especially, when divided molds are used to mold the seal member, a fin may be disposed in the seam portion by the seal member material running out of the mold, and when this fin is brought into contact with the chamber wall or opening by the twisting of the seal member, it may prevent the seal member from being pressed onto the wall or opening with uniform pressure, and may cause partial deterioration of the sealing performance.
Moreover, since the prior art valve body was designed to close and seal the opening of the gate disposed in a flat wall, the seal surface of the valve body was formed flat. However, the processing chamber disposed inside a vacuum vessel has a substantially cylindrical form, so if the valve body of the gate valve for sealing the gate leading to the processing chamber is shaped like a plate or the portion facing the gate is flat, the inner wall surface of the processing chamber becomes uneven, and the process performed within the processing chamber is affected thereby and becomes uneven. On the other hand, if the valve body is shaped to correspond to the inner wall surface shape of the processing chamber, the projection to be inserted into the opening must be disposed at the center of the valve body and the valve body must be moved within the opening for a distance corresponding to the height of the projection. Especially when the projection is disposed to correspond to a cylindrical wall, the valve body must be moved for a long distance, requiring an additional mechanism for moving the valve body for a long distance, which causes the apparatus to become larger, or causes the valve body to vibrate due to the interaction with the guide. Further, if a groove or dent according to the prior art must be disposed in the seal surface, the groove or dent must be disposed in the curved surface, which requires much work and time, increasing the manufacturing costs and deteriorating the efficiency. Furthermore, fitting the seal member into the groove or dent disposed in the curved surface may require long work time, which may also cause the local deterioration of the sealing performance.